Combined chair seat and backrest unit



FIG. 1 is a rear perspective view of a combined chair seat and backrest unit showing our design wherein a portion thereof has been omitted for convenience of illustration;

FIG. 2 is a side elevational view;

FIG. 3 is a top plan view; and,

FIG. 4 is a front perspective view thereof. 

The ornamental design for a combined chair seat and backrest unit, substantially as shown and described. 